In scientific studies and various applications, there is a need for a device to detect very small displacements in the position of an object with respect to a reference. Some state of the art methods to accomplish the foregoing include techniques associated with piezoresistive bridges, F. M. microphones, laser interference and fiber optics. These methods differ from one another in their operating power requirements, linearity and resolution of the desired data in low signal to noise environments. Characteristically, all of these methods involve fairly high voltage and/or current for operation, making them unsuitable in applications where only very low power is available. The need exists for a displacement transducer which can operate at low power levels, that is, of the order of 100 microamperes, has high linearity over a large dynamic range and is capable of resolving displacements down to a few hundred Angstroms. The acoustic detector of the present invention meets these criteria.